This study seeks to identify, characterize (where appropriate) and quantitate host factors associated with resistance to both enamel and root caries. The central strategy is the examination of specific components and properties of oral fluids and tooth deposits in adults who represent the extremes of caries activity. A major focus will be on various forms of pH regulation in plaque on both enamel and root surface. Enamel and cementum plaque will be studied in vitro and in vivo in caries resistant (CR) and susceptible subjects (CS) following application of sucrose, arginine, lysine and urea alone and in combination. pH will be measured and samples removed during the course of the experiments for quantitation of acids and various bases (ammonia, polyamines, total monoamines) using methods (mainly chromotographic) developed in this laboratory. Plaques from CR and CS will also be examined for protease activity and IgA antibody levels to specific S. mutans antigens (ELISA). Comparative studies of minor salivary gland secretions will include immunochemical quantitation of lysozyme and SIgA and specific IgA antibody (ELISA). Enamel and cementum pellicle deposits of various ages, removed by both chemical and mechanical means from CR and CS will be examined quantitatively for a spectrum of proteins using immunochemical techniques. The effect of salivary faractions (From CR and CS) on enamel and cementum demineralization will be examined in several in vitro model systems. Statistical evaluation of the overall data generated will enable us to develop characteristic profiles for CR and CS subjects. Elucidation of factors associated with caries resistance could result in development of new strategies for the prevention of caries.